Approximately 1.25 million new cases of breast cancer are diagnosed each year. In a majority of these cases, there is an urgent need for surgery to remove the tumor and to excise the sentinel lymph nodes and inspect them histologically to determine whether the cancer has spread to other sites in the body. The sentinel lymph nodes are the first nodes to receive lymphatic drainage from the tumor. They are called this because they reliably alert the clinician to any cancer spread. A sentinel lymph node biopsy is a standard of care in breast cancer operations today.
Locating sentinel nodes during surgery is difficult. One method for locating the sentinel node is to inject a dark blue dye into the lymphatic system in the breast. The dye then disperses throughout the breast lymphatic system and the surgeon removes any colored nodes. This method is recognized as being error-prone.
An improved method involves injecting a radioactive dye into the lymph nodes. In a similar manner, the dye drains through the lymphatic system and the surgeon then uses a radiation detector to help locate the sentinel nodes. However, the use of radioisotopes presents a significant, and an expensive, logistical burden, because of the need to allocate the time and resources of a nuclear medicine radiologist in addition to the surgeon for what is otherwise a routine operation. Further, many patients are reluctant to receive a radioactive injection. These factors can become a significant barrier to the use of radioisotopes to locate the sentinel nodes.
A further improved method involved injecting suspensions of magnetic particles into the lymph nodes and waiting for the magnetic particles to drain though the lymphatic system. The particles are then detected using a magnetometer, which reveals the location of the lymph nodes. See US2011/0133730. Prior art solutions, such as Sienna+®, have a very low osmolality of about 30 mOsm/kg. Sienna+® is an aqueous solution of maghemite nanoparticles coated in carboxydextran, having an iron concentration of about 25.5 to 29.5 mg/mL. It takes about 30 minutes for the magnetic particles in a Sienna+® injection to drain sufficiently through the lymphatic system to ensure accurate lymph node detection, which can potentially cause significant and costly downtime during surgical procedures. Consequently, impatient physicians may attempt to detect the lymph nodes too soon—i.e., before the magnetic particles have sufficiently drained through the lymphatic system—which could result in incomplete lymph node detection.
A need therefore exists for compositions that enable more efficient procedures.
The present invention addresses this need.